C-MAC

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For other uses, see C-MAC (disambiguation).
The simultaneous PAL transmission of all TV-picture elements and the multiplexed transmission of the TV picture elements with D2-MAC.
Simulated MAC signal. From left to right: digital data, chrominance and luminance

C-MAC is the variant approved by the European Broadcasting Union (EBU) for satellite transmissions. The digital information is modulated using 2-4PSK (phase-shift keying), a variation of quadrature PSK where only two of the phaser angles (±90°) are used.[1]

  • The data capacity for C-MAC is 3Mbit/s.
  • C-MAC data has to be sent to the transmitter separately from the vision.
  • The transmitter switches between FM (vision) and PSK (sound/data) modulation during each television line period.

C-MAC variants : E-MAC[edit]

E-MAC (Extended MAC) is 16:9 version of C-MAC. Originally E-MAC was designed for 15:9 pictures, it later adopted the 16:9 aspect ratio.

  • In E-MAC all the 4:3 information is transmitted exactly as in C-MAC so that C-MAC receivers are still compatible.
  • E-MAC hides extra luminance and chrominance information in the field blanking interval and parts of the line blanking interval.
  • E-MAC has a lower data capacity because luminance is hidden where data would usually be located.
  • A 'steering' signal is transmitted to indicate to the 16:9 receiver whereabouts the 4:3 picture information.
  • E-MAC receivers stitch the 4:3 and helper wide-screen data into a seamless 16:9 picture.

MAC FAQ[edit]

MAC transmits luminance and chrominance data separately in time rather than separately in frequency (as other analog television formats do, such as composite video).

Audio and Scrambling (selective access)

  • Audio, in a format similar to NICAM was transmitted digitally rather than as an FM sub-carrier.
  • The MAC standard included a standard scrambling system, Euro-Crypt, a precursor to the standard DVB-CSA encryption system.

See also[edit]

TV transmission systems

References[edit]

External links[edit]